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0LF (q-1)11-j-0a ' encountered In offsite wells MW-8 and MW-9 from grade to 11 feet bgs Figure 4 shows cross sections of the site based on lithologies noted during drilling activities ' 42 Groundwater Depth to groundwater has varied from approximately 6 feet to 11 feet bgs since the beginning of quarterly groundwater monitoring began In October 2003 (Table 3) During well ' installation activities groundwater was typically first encountered at approximately 9 feet bgs indicating that the groundwater aquifer is unconfined Soil samples collected from first encountered groundwater to 51 feet bgs (deepest well drilled) have generally been classified ' as very moist to wet, which indicates the presence of a single aquifer No evidence of confining layers has been encountered in soil borings or CPTs advanced at the site ' Shallow Wells Shallow wells (MW-1 through MW-5 and MW-7 through MW-9) are installed to a depth of 17 ' feet bgs with a 10-foot section of screen (Table 2) The shallow wells are installed in the upper portion of the aquifer that is dominated by silt to sandy silt In the wells onsite ' Deep Well The deep well (MW-6D) has been Installed at the site to a depth of 51 feet bgs with a 5-foot well screen from 46 to 51 feet bgs (Table 2) The well screen Is installed in silt The general hydraulic gradient at the site In both the shallow and deep zones (all one aquifer) has been consistently to the north / northwest A groundwater flow direction rose ' diagram depicting the groundwater flow direction since fourth quarter 2003 is included as Figure 5 (Table 5) and a Groundwater Elevation Contour Map for the third quarter 2004 has been Included as Figure 6 ' 5 0 PETROLEUM HYDROCARBON DISTRIBUTION AND CONCENTRATION TRENDS ' 5.1 Distribution of Hydrocarbons In Soil ' Benzene and TPHg were detected in minor amounts (maximum of 0 007 mg/kg benzene and 2 2 mglkg TPHg) In soil samples collected from under the former USTs but have not been detected in samples collected from any of the soil borings or from under any of the dispensers or product lines (Table 1) TAME and TBA were both detected in samples ' collected from the UST excavation and under the fuel dispensers and product lines (maximum of 0 11 mg/kg TAME and 52 mg/kg TBA), and were also detected immediately downgradient of the dispensers in MW-5 and MW-6D No concentrations of TAME or TBA ' were detected any of the other soil borings and they appear to be well delineated by EX-1 to the west, MW-4 to the east, MW-1 and MW-3 to the south, and by the deeper samples collected from MW-6D (Table 1) 1 MtBE Is the most pervasive dissolved hydrocarbon at the site and, as such, SECOR has plotted the MtBE concentrations detected in soil on Figures 7, 8, and 9 Figure 7 depicts the ' lateral extent of MtBE In soil from 0 to 9 5 feet bgs and Figure 8 depicts the lateral extent of 32262 Assessment&Feasibility Report&SCM doc 7 September 30,2004 ' 77EL 32262 04 0502